1. Field of the Invention
The present invention relates to an image display device, and more particularly, to an image display device in a digital TV that is capable of converting into various kinds of resolution by using single bit map data in the digital TV.
2. Background of the Related Art
Due to a rapid development of information communication, many people believe that a digital revolution is taking place. As the technologies on electricity, electron, computer and communication are being rapidly developed, the pattern in storing the information on image, audio and multimedia made by the collection of information of various shapes has been changed from an analog pattern to a digital pattern.
Particularly, with the development of an MPEG (Moving Picture Experts Group) technology as a compression standard for moving picture data requiring a relatively large amount of data, the digital image data is gradually being decreased in size.
The MPEG technology is applied in the fields such as computers, broadcasting, electric appliances, communication and the like, thereby providing digital video and audio service. So as to provide such the digital video and audio service, digital equipment is proposed.
Among the digital equipments, a TV is one of the important media for easily and effectively providing information in everyday life.
Based upon such the digital technology, a digital TV compresses video data and audio data with the MPEG technology and transmits the resulting data, such that a great amount of information data can be provided in faster and stable manners. Thereby, the digital TV can have a large number of broadcasting channels that provide an improved quality of image and sound to a user.
Therefore, the digital TV can increase data capacity by 4 to 8 times when compared with the existing analogy TV, thereby allowing more services covering various fields such as sports, movie, home shopping, music and so on.
At present, the digital TV has provided the image service covering cable broadcasting, video on demand (VOD) and the like, in addition to public waves.
Also, a TV viewer selects a desired service in accordance with his own preference, thereby enjoying a free channel selection. Moreover, the viewer can select his desired broadcasting from numerous channels provided on the digital TV.
As noted above, the digital TV has various additional functions for the purpose of fulfilling various preferences of the viewers and thus providing much convenience to them.
In case of an output device of a setop box for a digital TV, generally, when predetermined information is provided to a user or when set contents and functions of the TV are changed, that is, when the set contents such as input set, display set, audio set, etc. are changed, the output device adopts a changing method using an on-screen display (OSD) where the set contents to be changed are displayed on the screen of TV.
Moreover, the image display device is applicable to data broadcasting in the digital TV.
The data broadcasting is carried out with texts that are contained in broadcasting data and thus transmitted, for the purpose of embodying various kinds of additional images.
For example, the data broadcasting outputs daily program order with the image during broadcasting or outputs an additional explanation on the image being broadcast.
FIG. 1 illustrates a conventional image display device in a digital TV.
As shown, the image display device is comprised of a memory 101 in which image data and text data are stored, an image outputting part 102 for reading the image data from the memory 101, and a display processing part 103 for reading the text data from the memory 101 and mixing the image data and the text data.
The image display device further includes an analog/digital converter 104 for converting analog image data into digital image data.
In operation, the conventionally developed image display device in the digital TV receives each of the text data and image data of an arbitrary digital broadcasting such as public wave broadcasting, cable broadcasting and video on demand at the digital TV, decodes the text data and the image data, respectively and stores the decoded data in the memory 101.
Before storing in the memory 101, at this time, each of the text data and the image data may be converted into bit map data.
Thereby, the image outputting part 102 reads the image data from the memory 101.
The display processing part 103 mixes the text data read from the memory 101 and the image data and outputs the mixed result on a predetermined display screen.
When predetermined information is provided to a user, when set contents and functions of the TV are changed or when various images are provided with the text data, of course, the display processing part 103 mixes the text data (i.e., bit map data) read from the memory 101 and the image data (i.e., bit map data) and outputs the mixed result on the predetermined display screen. On the other hand, when the text data is not provided, the display processing part 103 outputs only the image data on the screen.
Also, the digital TV may receive analog broadcasting, in addition to the digital broadcasting.
That is to say, the digital TV receives analog image data of the analog broadcasting, converts the analog image data into digital image data through the analog/digital converter 104, and decodes the converted digital image data. Then, it stores the decoded result to the memory 101 and after that, executes the same process as the digital broadcasting.
On the other hand, the digital TV can handle the image having various frame rates in interlace and progressive scanning of 24 Hz, 30 Hz, 60 Hz and so on and display various images having resolution of 720×480, 854×480, 1280×720 and 1920×1080.
To provide the various resolution as mentioned above, the image data and the text data should be convertible according to variation of the resolution.
However, the above-mentioned conventional image display device can convert the image data into display format according to the variation of resolution and display it, but it does not have any function of converting the text data into the display format according to the variation of resolution. So, the conventional device should store the text data for each resolution in bit map data format and read the bit map data stored according to each resolution, thereby displaying the resulting data on the screen.
An example of various resolution in the digital TV is given by the following Table.
Display ResolutionBit Map Type1920 × 10801600 × 9601280 × 720 1280 × 720854 × 480 800 × 480720 × 480 720 × 480
In other words, in order to output the text data for the above-listed four resolution, for example, 720×480, 854×480, 1280×720 and 1920×1080, the above-listed four bit map data, for example, 1600×960, 1280×720, 800×480, and 720×480, corresponding to the four resolution must be stored in the memory 101, such that the image display device displays a predetermined image.
At this time, the bit map data has the data size corresponding to the value obtained by multiplying the number of dots according to the resolution by the number of colors supported.
In other words, if the resolution of 720×480 and the color of 16 bits are provided, the bit map data has the data size of 5,529,6 Kbits (720×480×16=5,529,6)
Therefore, the conventional image display device has to store the bit map data corresponding to the kinds of the resolution, in order to display the image according to each resolution, and the bit map data has a substantially large data size as the resolution is high.
Additionally, the bit map data in the conventional image display device is not compressed, thereby resulting in the occupation of a large memory space.